In conventional power modules, power semiconductor chips, insulating substrates, and heat sinks are laminated. Specifically, an insulating substrate is formed of a plate-shaped insulating member having metal layers on both main surfaces, a power semiconductor chip is bonded to one of the metal layers and a heat sink is bonded to the other metal layer. One of the metal layers is formed into a predetermined pattern also having a portion that provides wiring in addition to the portion to which the power semiconductor chip is bonded.